The egg, which was 21 days into its 30-day gestation period, was taken from Little Barrier kakapo Heather because she had two eggs and removing one would give a second chick a better rate of survival.

Eggs were more likely to be damaged on the nest if there was more than one egg and if both chicks hatched, one would not get the support from its mother it needed.

Rangers waited for the mother kakapo to go feeding during the night, then swooped in for the egg.

It was flown to Codfish Island in a portable incubator encased in a polystyrene container full of cotton wool.

There were about six potential kakapo mothers on Codfish Island who were sitting on non-fertile eggs.

Rangers were watching to see how well the kakapo were sitting on the eggs before deciding which would become the adopted mum of the new addition.

Kakapo Recovery Programme manager Deidre Vercoe Scott said it was a long way to transfer an egg but it was better than the alternative. Breeding on the two secure islands would see the long-term security of the kakapo population.

The first kakapo chick - Lisa One - to hatch anywhere in three years emerged from a cracked egg held together by tape and glue on Codfish Island last week.